Bruce G. Peterjohn
U.S. Fish and Wildlife Service
Office of Migratory Bird Management
Laurel, Maryland 20708
and
John R. Sauer
U.S. Fish and Wildlife Service
Patuxent Wildlife Research Center
Laurel, Maryland 20708

Abstract. The North American Breeding Bird Survey
(BBS) was used to estimate continental and regional changes in bird
populations during 1989-1990 and 1990-1991, placing these short-term
changes within the context of population trends since 1966. For the
entire survey area, 51.7% of the species exhibited increases in population
size during 1989-1990, reversing the decreasing tendency exhibited by
the majority of species during 1988-1989. A similar percentage (51.4%)
of species with increasing populations was noted during 1990-1991. These
percentages were also analyzed for 12 guilds of North American birds
and 3 broad geographical regions. Many regional patterns exist in these
population changes, reflecting the variability inherent in short-term
population fluctuations. Two-year (1989-1990 and 1990-1991) changes
and long-term (1966-1990) continental trends are provided for 255 species.